The judge said that if the jury decides he did kill Mrs Yates they would then have to decide if the partial defence of diminished responsibility would apply to that death.

He said it was agreed by both the prosecution and the defence that Farrow had a psychopathic personality disorder.

It is the defence case that this abnormal mental function "substantially affected" his ability to exercise self control, he said, and it was up to the jury to decide if this had been proved.

The judge added that both psychiatrists who gave evidence in court said being a psychopath would not have affected Farrow's ability to understand the nature of his conduct or his ability to form rational judgement.

'Adept liar'

He said that it was not disputed that Farrow had told a mental health nurse after his arrest that "I killed her", and it was also agreed that the defendant was an "adept liar".

The judge said it was for the jury to decide whether that "confession" was reliable evidence of guilt.

He said it was the case of the prosecution that there were similar features in both killings; the windows were covered at Mrs Yates cottage and the vicarage, there was no forced entry of either property and both victims were stabbed.

Evidence of similarities was not enough to convict by itself, the judge said, but he asked jurors whether there were sufficient similarities for it to count as additional weight in the prosecution's case.

He added that the defence had pointed out differences such as the vicarage being ransacked but Mrs Yates' cottage was not.